Patients with chronic congestive heart failure will be assessed in regard to hemodynamic abnormalities (left ventricular function, systemic vascular resistance, blood volume, forearm and hepatic blood flow, venous compliance) in relation to circulating levels of catecholamines (primarily norepinephrine) and plasma renin activity. The effect on hemodynamics and blood hormone levels of orthostasis, lower body negative pressure, exercise, salt depletion, and administration of various vasodilator and blocking drugs will be assessed. Normal responses to these interventions will be evaluated in normal volunteers. Dogs with myocardial damage induced by DC countershock will also be monitored for the relationship between hemodynamic abnormalities and blood catecholamines and renin activity. The response to exercise and to vasodilator and blocking drugs will be studied in normal and left ventricular-damaged dogs. Studies in normal dogs will be carried out to evaluate the relationship between exogenously administered or endogenously produced norepinephrine and angiotensin on the vascular response to vasodilator drugs.